Sensors, electrochemical amperometric

Figure 1.11 — Average number of papers on (bio)chemical sensors published annually, based on data from Janata s biannual review. E electrochemical sensors ISEs ion-selective electrodes P potentiometric sensors A amperometric sensors C conductimetric sensors O optical sensors M mass sensors T thermal sensors. (Adapted from [23] with permission of the American Chemical Society).

There are three types of electrochemical sensors potentiometric, amperometric, and potentiodynamic sensors. 

Electrochemical sensors include amperometric cells, especially galvanic fuel cells, and polarographic cells. Both types are available from several manufacturers world-wide in large numbers for clinical use. Higher stability with fewer technical problems makes the galvanic cell currently the most popular oxygen sensor in the operating room environment [12]. 

The current-potential relationship of an electrochemical ceU provides the basis for voltammetric sensors. Amperometric sensors, that are also based on the current-potential relationship of the electrochemical cell, can be considered a subclass of voltammetric sensors. In amperometric sensors, a fixed potential is applied to the electrochemical cell, and a corresponding current, due to a reduction or oxidation reaction, is then obtained. This current can be used to quantify the species involved in the reaction. The key consideration of an amperometric sensor is that it operates at a fixed potential. However, a voltammetric sensor can operate in other modes such as linear cyclic voltammetric modes. Consequently, the respective current potential response for each mode will be different. 

Several decades of industrialization have changed the enviromnent drastically, leading to all sorts of pollution. Water pollution, being one of most important issues related to daily life, has always been addressed and mtmitored by various means of analytical tools. Different electrochemical sensors for the detection of pollutants in water have been well established, which can be categorized into the following (i) poten-tiometric sensors, (ii) amperometric sensors, (iii) voltammetric sensors, and (iv) conductometric sensors. In this chapter, we will introduce the fundamentals, applications, advantages, limitations, and recent trends for the development of each type of sensors. 

An electrochemical sensor is essentially an electrochemical cell consisting of two or more electrodes in contact with a solid electrolyte. They can be classified according to their operation mode, e.g., conductivity/impedance sensors, potentiometric sensors, and amperometric sensors. 

Compared to electrochemical enzymatic detection, it can be said that affinity-based interactions help us monitor assays that are more complex (Wang, 2006). Electrochemical techniques are very proper techniques to follow the biorecognition events in affinity-based sensors. Although amperometric detection is more practical relative to EIS, especially for monitoring the changes at the electrode surface, EIS is preferred (Lafleur et al., 2016). 

Electrochemical sensors play a crucial role in environmental and industrial monitoring, as well as in medical and clinical analysis. The common feature of all electroanalytical sensors is that they rely on the detection of an electrical property (i.e., potential, resistance, current) so that they are normally classified according to the mode of measurement (i.e., potentiometric, conductometric, amperometric). A number of surveys have been published on this immense field. The reader may find the major part of the older and recent bibliography in the comprehensive reviews of Bakker et al. [109-111]. Pejcic and De Marco have presented an interesting survey... 

Based on many of the advances described above in electrochemical approaches to immunoassay, it is tempting to conclude that commercialization of some of the approaches is imminent. This may be true, but the historical use of optical methods for many clinical chemistry tests coupled with their rapidly growing use in immunoassay is a difficult barrier for any radically different method to overcome, though electrochemical sensors have become more important in the clinical chemistry laboratory over the last decade. In any event, to be successful ECIA methods will have to demonstrate clear superiority over existing and emerging technologies in both cost and performance. Some of the more recently described approaches such as those using enzyme amplified amperometric detection and ecLIA appear... 

D.R. Shankaran and S.S. Narayanan, Amperometric sensor for thiols based on mechanically immobilised nickel hexacyanoferrate modified electrode. Bull. Electrochem. 17, 277-280 (2001). 

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